The present invention relates to nonionic X-ray contrast media.
For a satisfactory portrayal of the organs of the urinary tract, the vascular system, the cerebrospinal cavities and other systems, X-ray contrast media must be administered in high dosage. Accordingly, highly concentrated contrast media solutions are required. In turn, the physicochemical properties of these solutions, such as solubility, viscosity, and osmotic pressure, are of great importance. It is possible, for example, for highly concentrated, nonionic contrast media solutions to exhibit, due to their low osmotic pressure, markedly advantageous compatibility over ionic contrast media solutions. Furthermore, X-ray contrast media for angiography, urography, myelography, etc., must be extraordinarily highly water-soluble.
Metrizamide (U.S. Pat. No. 3,701,771) can be cited as the first, well compatible, soluble, nonionic opacifying compound suitable for practical radiology. In metrizamide, solubility is due, just as for ioglunide (GB No 1,436,357) to a polyhydroxyalkyl residue joined via an acid amide bond to a triiodinated aromatic. Compounds of this type, in addition to being difficult to manufacture, are not sufficiently stable for sterilization under heat, and also have an inadequate shelf life. These properties are a grave disadvantage for their practical use in X-ray contrast media.
Also, among the known derivatives based on triiodaminophthalic acid amides, only a very few proved to be of sufficient compatibility and chemical stability for use as opacifiers in X-ray contrast media for intravasal application. In these compounds, the amide groups in the 1- and 3-positions are substituted symmetrically, i.e., both carboxy groups are amidated with the same amine. (U.S. Pat. No. 4,001,323 and GB Pat. No. 1,548,594).